Investigating lysozyme amyloid fibril formation and structural variability dependence on its initial folding state under different pH conditions.

Protein fibril formation and accumulation are associated with dozens of amyloidoses, including the widespread and yet-incurable Alzheimer's and Parkinson's diseases. Currently, there are still several aspects of amyloid aggregation that are not fully understood, which negatively contributes to the development of disease-altering drugs and treatments. One factor which requires a more in-depth analysis is the effect of the environment on both the initial state of amyloidogenic proteins and their aggregation process and resulting fibril characteristics. In this work, we examine how lysozyme's folding state influences its amyloid formation kinetics and resulting aggregate structural characteristics under several different pH conditions, ranging from acidic to neutral. We demonstrate that both the initial state of the protein and the solution's pH value have a significant combined effect on the variability of the resulting aggregate secondary structures, as well as their stabilities, interactions with amyloid-specific dye molecules, and self-replication properties.

Conformation-Specific Association of Prion Protein Amyloid Aggregates with Tau Protein Monomers.

Protein aggregation into amyloid fibrils is associated with several amyloidoses, including neurodegenerative Alzheimer's and Parkinson's diseases. Despite years of research and numerous studies, the process is still not fully understood, which significantly impedes the search for cures of amyloid-related disorders. Recently, there has been an increase in reports of amyloidogenic protein cross-interactions during the fibril formation process, which further complicates the already intricate process of amyloid aggregation. One of these reports displayed an interaction involving Tau and prion proteins, which prompted a need for further investigation into the matter. In this work, we generated five populations of conformationally distinct prion protein amyloid fibrils and examined their interaction with Tau proteins. We observed that there was a conformation-specific association between Tau monomers and prion protein fibrils, which increased the aggregate self-association and amyloidophilic dye binding capacity. We also determined that the interaction did not induce the formation of Tau protein amyloid aggregates, but rather caused their electrostatic adsorption to the prion protein fibril surface.

Rapid restructurization of conformationally-distinct alpha-synuclein amyloid fibrils at an elevated temperature.

Protein aggregation in the form of amyloid fibrils is linked with the onset and progression of more than 30 amyloidoses, including multiple neurodegenerative disorders, such as Alzheimer's or Parkinson's disease. Despite countless studies and years of research, the process of such aggregate formation is still not fully understood. One peculiar aspect of amyloids is that they appear to be capable of undergoing structural rearrangements even after the fibrils have already formed. Such a phenomenon was reported to occur in the case of alpha-synuclein and amyloid beta aggregates after a long period of incubation. In this work, we examine whether incubation at an elevated temperature can induce the restructurization of four different conformation alpha-synuclein amyloid fibrils. We show that this structural alteration occurs in a relatively brief time period, when the aggregates are incubated at 60 °C. Additionally, it appears that during this process multiple conformationally-distinct alpha-synuclein fibrils all shift towards an identical secondary structure.

Lysozyme Amyloid Fibril Structural Variability Dependence on Initial Protein Folding State.

Amyloid fibril formation is associated with several amyloidoses, including neurodegenerative Alzheimer's or Parkinson's diseases. The process of such fibrillar structure formation is still not fully understood, with new mechanistic insights appearing on a regular basis. This, in turn, has limited the development of potential anti-amyloid compounds, with only a handful of effective cures or treatment modalities available. One of the multiple amyloid aggregation factors that requires further examination is the ability of proteins to form multiple, structurally distinct aggregates, based on the environmental conditions. In this work, we examine how the initial folding state affects the fibrilization of lysozyme-an amyloidogenic protein, often used in protein aggregation studies. We show that there is a correlation between the initial state of the protein and the aggregate formation lag time, rate of elongation, resulting aggregate structural variability and dye-binding properties, as well as formation lag time and rate of elongation.

Superoxide dismutase-1 alters the rate of prion protein aggregation and resulting fibril conformation.

The assembly of amyloidogenic proteins into highly-structured fibrillar aggregates is related to the onset and progression of several amyloidoses, including neurodegenerative Alzheimer's or Parkinson's diseases. Despite years of research and a general understanding of the process of such aggregate formation, there are currently still very few drugs and treatment modalities available. One of the factors that is relatively insufficiently understood is the cross-interaction between different amyloid-forming proteins. In recent years, it has been shown that several of these proteins or their aggregates can alter each other's fibrillization properties, however, there are still many unknowns in the amyloid interactome. In this work, we examine the interaction between amyloid disease-related prion protein and superoxide dismutase-1. We show that not only does superoxide dismutase-1 increase the lag time of prion protein fibril formation, but it also changes the conformation of the resulting aggregates.

Interplay between epigallocatechin-3-gallate and ionic strength during amyloid aggregation.

The formation and accumulation of protein amyloid aggregates is linked with multiple amyloidoses, including neurodegenerative Alzheimer's or Parkinson's disease. The mechanism of such fibril formation is impacted by various environmental conditions, which greatly complicates the search for potential anti-amyloid compounds. One of these factors is solution ionic strength, which varies between different aggregation protocols during in vitro drug screenings. In this work, we examine the interplay between ionic strength and a well-known protein aggregation inhibitor-epigallocatechin-3-gallate. We show that changes in solution ionic strength have a major impact on the compound's inhibitory effect, reflected in both aggregation times and final fibril structure. We also observe that this effect is unique to different amyloid-forming proteins, such as insulin, alpha-synuclein and amyloid-beta.

Polymorphism of Alpha-Synuclein Amyloid Fibrils Depends on Ionic Strength and Protein Concentration.

Protein aggregate formation is linked with multiple amyloidoses, including Alzheimer's and Parkinson's diseases. Currently, the understanding of such fibrillar structure formation and propagation is still not sufficient, the outcome of which is a lack of potent, anti-amyloid drugs. The environmental conditions used during in vitro protein aggregation assays play an important role in determining both the aggregation kinetic parameters, as well as resulting fibril structure. In the case of alpha-synuclein, ionic strength has been shown as a crucial factor in its amyloid aggregation. In this work, we examine a large sample size of alpha-synuclein aggregation reactions under thirty different ionic strength and protein concentration combinations and determine the resulting fibril structural variations using their dye-binding properties, secondary structure and morphology. We show that both ionic strength and protein concentration determine the structural variability of alpha-synuclein amyloid fibrils and that sometimes even identical conditions can result in up to four distinct types of aggregates.

Temperature-Dependent Structural Variability of Prion Protein Amyloid Fibrils.

Prion protein aggregation into amyloid fibrils is associated with the onset and progression of prion diseases-a group of neurodegenerative amyloidoses. The process of such aggregate formation is still not fully understood, especially regarding their polymorphism, an event where the same type of protein forms multiple, conformationally and morphologically distinct structures. Considering that such structural variations can greatly complicate the search for potential antiamyloid compounds, either by having specific propagation properties or stability, it is important to better understand this aggregation event. We have recently reported the ability of prion protein fibrils to obtain at least two distinct conformations under identical conditions, which raised the question if this occurrence is tied to only certain environmental conditions. In this work, we examined a large sample size of prion protein aggregation reactions under a range of temperatures and analyzed the resulting fibril dye-binding, secondary structure and morphological properties. We show that all temperature conditions lead to the formation of more than one fibril type and that this variability may depend on the state of the initial prion protein molecules.

Using lysozyme amyloid fibrils as a means of scavenging aggregation-inhibiting compounds.

The aggregation of amyloidogenic proteins is linked to several amyloidoses, including neurodegenerative disorders, such as Alzheimer's or Parkinson's disease. Currently there are very few effective cures or treatments available, despite countless screenings and clinical trials. One of the most challenging aspects of potential anti-amyloid drug discovery is finding which molecules are the actual inhibitors out of mixtures, which may contain hundreds of distinct compounds. Considering that anti-amyloid compounds would interact with the aggregate, this affinity could be used as a means of separating such compounds from ineffective ones. In this work, we attempt to scavenge potential aggregation-inhibiting molecules out of four, different complexity mixtures, ranging from oxidized gallic acid to tea extract, using lysozyme amyloid fibrils. We show that these compounds bind to aggregates with high affinity and can be later separated from them by different methods.